OBJECTIVES/AIMS This prospective, randomized, controlled trial will measure the effectiveness of two interventions encouraging people with symptoms of an acute myocardial infarction (MI) to call 911 and to seek medical care early. The achievement of these objectives can lead to a community-wide reduction in mortality from AMI. RATIONALE Heart disease is the leading cause of death among adults in the United States. Data collected in Seattle/King County over the last three years have shown that people with AMI delay two hours from the onset of symptoms to calling for help and that only 45% call 911. With the availability of thrombolytic therapy, and the growing ability of paramedics around the country to diagnose an AMI in the prehospital setting, death and disability from a heart attack can be significantly reduced if people seek medical care early and call 911. DESIGN A population-based household intervention and a targeted high-risk individual intervention will be compared. For the household intervention, the heads of households over 50 will receive multiple mailings of one of three different messages. The individual intervention, which is targeted to persons who are at high risk of a heart attack (persons hospitalized in coronary care units), will be divided into two groups. One group will receive a personalized mailing and the second group will receive a mailing plus a phone call from a public health nurse. Both interventions will run concurrently for one year, and each will have a control group receiving no intervention. Preceding these interventions will be a community-wide awareness campaign using television and radio. OUTCOMES We will determine whether there is an increase in the use of 911 and a decrease in the duration of symptoms and which intervention is most effective. Outcomes will be determined by a community-wide 19 hospital surveillance system.